The present invention relates generally to a display driver for a visual display. More particularly, the present invention relates to a circuit that provides drive signals to a color display, such as, a liquid crystal display (LCD).
In conventional display systems, such as, color liquid crystal display (LCD) systems, a matrix of pixels can provide static or dynamic visual images in color. Each pixel is typically comprised of three primary color elements, such as, a red element, a green element, and a blue element. Each color element is controlled by an associated transistor. The matrix of pixels is associated with a matrix of transistors, such as, thin film transistors (TFTs) arranged in rows and columns.
A column line is coupled to the drain or source associated with each transistor in each column. A row line is coupled to the gate associated with each transistor in each row. A row of transistors is activated by providing a gate control signal to the associated row line. The gate control signal turns on each transistor in the row. Each transistor in the row provides an analog voltage associated with its column line to cause the color element to emit a particular amount of light. Generally, a column driver circuit selects from the same set of analog voltages to provide an analog voltage for each color element in the display (e.g., the three color elements in each pixel each receive one analog voltage level from the same set of voltage levels). The analog voltage is provided to the column line so that the appropriate amount of light, e.g., color is emitted by each pixel.
Transmission versus voltage characteristics for the three color elements (e.g., the primary color elements) vary from each other. Accordingly, conventional systems which utilize the same voltages to drive the three color elements can be susceptible to undesirable color shifts. The undesirable color shifts are ascertainable as the analog voltages or gray scale values for each pixel are varied. Gray scale values refer to the range from darkness to lightness for each pixel or color element on a display.
Conventional LCDs attempt to reduce color-shift problems by having a large number of gray scale values (large gray scale capability). With such a scheme, a particular gray scale value can be selected from the large number of gray scale values available to yield the closest match to a desired response for the particular color being driven on the LCD. However, this technique creates a computational burden on the graphic system because the gray scale signal for each pixel must be individually processed to determine which gray scale value provides the most appropriate response. Further, this technique forces a compromise between the actual response and the desired response. This technique is also disadvantageous because it requires that a large number of gray scale values be available, thereby making the voltage driver larger, more complex, more costly, and less power efficient.
Thus, there is a need for a voltage driver circuit for a display that is not as susceptible to undesirable color shifts. Further, there is a need for a LCD which does not utilize the same analog voltage for each primary color element. Further still, there is a need for a new method of driving primary colors separately to provide a full set of gray scale values.
The present invention relates to a driver for a color display having an array of pixels. Each pixel includes a first color element, a second color element, and a third color element that is coupled to a first set of color terminals, a second set of color terminals, and a third set of color terminals, respectively. The driver includes an input circuit and a control circuit. The input circuit includes a first set of input terminals, a second set of input terminals, and a third set of input terminals. The first set of input terminals receives first color signals indicative of first gray scales for the first color element. The second set of input terminals receives second color signals indicative of second gray scales for the second color element, and the third set of input terminals receives third color signals indicative of third gray scales for the third color element. The control circuit is coupled to the input circuit and provides first analog signals in accordance with the first gray scales to the first set of color terminals. The control circuit also provides second analog signals in accordance with second gray scales to the second set of color terminals and provides third analog signals in accordance with the third gray scales to the third set of color terminals.
The present invention further relates to a voltage driver circuit for a color liquid crystal display having an array of transistors arranged in at least a first row, a second row, a first color 1 column, a first color 2 column, a first color 3 column, a second color 1 column, a second color 2 column, a second color 3 column. Transistors in the first color 1 column are coupled to a first color 1 column line; the transistors in the second color 1 column are coupled to a second color 1 column line, and the transistors in the first color 2 column are coupled to a first color 2 column line. The transistors in the second color 2 column line are coupled to a second color 2 column line, the transistors in the first color 3 column are coupled to a first color 3 column line, and the transistors in the second color 3 column are coupled to a second color 3 column line. The voltage driver circuit includes an input circuit and a control circuit that is coupled to the input circuit. The input circuit functions for receiving a first color 1 signal for the first color 1 column line, for receiving a first color 2 signal for the first color 2 column line, for receiving a first color 3 signal for the first color 3 column line, for receiving a second color 1 signal for the second color 1 column line, for receiving a second color 2 signal for the second color 2 column line, and for receiving a second color 3 signal for the second color 3 column line. The control circuit provides a first analog color 1 signal in accordance with the first color 1 signal, a first analog color 2 signal in accordance with the first color 2 signal, a first analog color 3 signal in accordance with the first color 3 signal, a second analog color 1 signal in accordance with the second color 1 signal, a second analog color 2 signal in accordance with the second color 2 signal, and a second analog color 3 signal in accordance with the second color 3 signal.
The present invention still further relates to a color liquid crystal display including an array of transistor and a control means. The array of transistors is arranged in at least a first row, a second row, a first red column, a first green column, a first blue column, a second red column, a second green column, and a second blue column. The transistors in the first red column are coupled to a first red column line; the transistors in the second red column are coupled to a second red column line, and the transistors in the first green column are coupled to a first green column line. The transistors in the second green column are coupled to a second green column line; the transistors in the first blue column are coupled to a first blue column line, and the transistors in the second blue column are coupled to a second blue column line. The control means provides a first analog red signal in accordance with a first red level, a first analog green signal in accordance with a first green level, a first analog blue signal in accordance with a first blue level, a second analog red signal in accordance with a second red level, a second analog green signal in accordance with a second green level, and a second analog blue signal in accordance with a second blue level.